C++ POCO - How to beautify a JSON?
As @Dmitry said on the comments, the parameters on the stringify() method would do:
static void stringify( const Dynamic::Var & any, std::ostream & out, unsigned int indent = 0, int step = - 1, int options = Poco::JSON_WRAP_STRINGS);Example:
Poco::JSON::Stringifier::stringify(json, oss, 4, -1, Poco::JSON_PRESERVE_KEY_ORDER);